This application generally relates to three-dimensional (3-D) imaging, and more particularly, to surface contour measurement using partial-coherence speckle interference tomography.
In the fields of counter-insurgency, counter-terrorism and law enforcement there is a need to identify and track suspects from a distance, without the suspect's knowledge or cooperation.
Single-view passive sensors typically do not procure 3-D data and thus cannot provide measurement and recognition of 3-D spatial features. And, while conventional 3-D laser radar (ladar) sensors exist which use direct detection pulse-echo ranging techniques, these sensors typically do not have the range resolution necessary to measure the full topography of a human face. Coherent ladar sensors have demonstrated adequate resolution and range. Yet, coherent ladar sensors are relatively large, very complex due to the coherent source and heterodyne processing, and are quite expensive.
In addition, structural lighting profilometry has been proposed that uses one or more planar sheets of light to illuminate the target and an imaging sensor located some distance away from the source such that the parallax viewing angle produces a spatial profile of the target indicative of the depth. However, a disadvantage of this approach is that the source and receiver must be located at some baseline distance away from each other in order to produce the parallax viewing angle and that the required baseline distance increases with target range.
These conventional approaches thus have been impractical for remote, covert biometric feature capture and identification of a suspect.